Fix assertion in hide all popovers until

[josepharhar]

This PR prevents an assertion from being hit in hide all popovers until by changing the conditions in which hide all popovers until gets called by the hide popover algorithm to use the opened in popover mode instead of looking at the current value of the popover attribute.

Fixes #10996

• At least two implementers are interested (and none opposed):
  • Chromium, gecko, and webkit all already pass the WPTs
• Tests are written and can be reviewed and commented upon at:
  • https://wpt.fyi/results/html/semantics/popovers/popover-attribute-basic.html
  • https://wpt.fyi/results/html/semantics/popovers/popover-change-type.html
• Implementation bugs are filed:
  • Chromium: N/A, already implemented
  • Gecko: N/A, already implemented
  • WebKit: N/A, already implemented
• Corresponding HTML AAM & ARIA in HTML issues & PRs: N/A
• MDN issue is filed: Not needed for this change
• The top of this comment includes a clear commit message to use.

(See WHATWG Working Mode: Changes for more details.)

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/popover.html ( diff )

[domenic]

Thanks, this looks good to me!

Can you fill out the OP? I think most of it will be N/A, and based on the discussion in #10996 I suspect many tests already cover this code path, but I would like to have that confirmed.

[josepharhar]

I verified that the assert gets hit in two tests if I undo this spec change change in chromium. I added them to the OP and filled out the rest. Thanks!